The present invention relates generally to refrigerated display merchandisers of the type used in supermarkets, mini-marts, convenience stores and other commercial establishments for displaying and merchandising refrigerated or frozen products for sale. More particularly, the present invention relates to open-front refrigerated display merchandisers of the type wherein a curtain of cold refrigerated air is passed downwardly across the open front product display region of the merchandiser.
Refrigerated display merchandisers, also commonly referred to as display cases, having open front display regions are commonly used in supermarkets, mini-marts, convenience stores and other commercial establishments for displaying and merchandising refrigerated or frozen products for sale. The open front nature of such display cases permits the consumer to simply reach into the product display region to select and remove a product for purchase without the inconvenience of needing to open a door to access the product. Customarily, a curtain of cold refrigerated air is passed downwardly at a relatively high velocity across the open front of the display case to form an invisible boundary between the product display region and the region of the store in front of the display case. This air curtain not only helps retain cool refrigerated air within the product display region of the display case, thereby cooling the display product on the shelves of the display case, but also functions to isolate, to a certain extent, the product display region from the ambient air within the store. Ambient air that does enter into open product display region undesirably causes increased energy consumption by increasing the cooling demand on the refrigeration system associated with the display case. Further, such ambient air may also cause a local temperature rise within the product display region sufficient to result in an undesirable rise in product temperature that could adversely impact upon product quality.
A problem encountered with when passing a curtain of refrigerated air downwardly across the open front of the product display region of the display case lies in the entrainment of ambient air into the stream of refrigerated air forming the air curtain. Turbulence exists at the boundary between the relatively high velocity curtain air and the generally quiescent ambient air lying in front of the display case. As a result of such turbulence, some ambient air is undesirably entrained into the air curtain. Multiple air curtain display cases have been developed in the prior art to address this entrainment problem. For example, display cases having two adjacent, parallel, but independently generated, air curtains of refrigerated air are common in the art. Typically, such as disclosed by Maehara in U.S. Pat. No. 4,633,677, the outermost air curtain has a slightly higher temperature than the innermost air curtain, so as to protect the colder innermost air curtain from the impact of ambient air entrainment. However, such designs do not completely eliminate the intrusion of ambient air into the refrigerated air curtain.
Also, it is well known in the art to establish a third air curtain of relatively high velocity ambient air outwardly of one or two refrigerated air curtains as a means of reducing entrainment of ambient air from the store into the refrigerated air curtains. Abraham, in U.S. Pat. No. 4,267,706, discloses establishing an ambient air curtain outwardly of an innermost refrigerated air curtain, with the outer ambient air curtain being directed downwardly parallel to and adjacent to the inner refrigerated air curtain. Beckwith et al, in U.S. Pat. Nos. 3,648,482 and 3,850,003, MacMaster et al, in U.S. Pat. No. 3,827,254 and Roberts, in U.S. Pat. No. 5,345,778, each disclose establishing an ambient air curtain outwardly of a pair of refrigerated air curtains. The curtain closest the product display region of the display case is coolest, while the center curtain is at a temperature slightly warmer than the innermost curtain, but substantially cooler than the outermost ambient air curtain. The center curtain of warmer refrigerated air serves to buffer the innermost colder refrigerated air curtain from warm air intrusion from the outermost ambient air curtain. The outermost curtain of ambient air is directed substantially vertically downwardly, either parallel to and adjacent the center air curtain or slightly inwardly toward the center air curtain, so as to preclude refrigerated air from the center and innermost refrigerated air curtains from spilling out of the product display region of the display case. The outermost ambient air curtain itself ideally spills into the store near the base of the display case so as to not be drawn into the air return inlets through which the refrigerated air curtains return to the evaporator compartment. Although generally quite effective in reducing intrusion of ambient air into the colder innermost refrigerated air curtain, some intrusion into the center refrigerated air stream will occur. Further, providing three separate air flow circuits fro generating the three independent air streams increases the complexity and cost of the display case. Consequently, a need exists for a refrigeration system that addresses the problem encountered by the interaction of warm air outside of the display case and the air curtain without significant expense.
Accordingly, it is an object of the present invention to provide a refrigerated merchandiser including an improved performance multi-layer air curtain system. It is a further object of the present invention to provide a refrigerated merchandiser including a multi-layer air curtain system that is relatively less expensive than other multi-layer air curtain refrigerated merchandisers.
The refrigerated merchandiser of the present invention includes a display defining a product display region having an open-front isolated from the ambient air of the store by means of a downwardly directed inner air curtain of relatively cold refrigerated air and a downwardly directed outer air curtain of relatively warmer air. In accordance with the present invention, the outer curtain of relatively warmer air is directed downwardly and outwardly away from the inner air curtain of relatively cold air at a divergent angle with respect to the inner air curtain. In a preferred embodiment, the outer air curtain of relatively warmer air is directed downwardly and outwardly away from the inner air curtain at a divergent angle of about 5 degrees to about 55 degrees, and more advantageously at a divergent angle of about 25 degrees to about 50 degrees, and even more advantageously at an angle about 35 degrees to about 45 degrees.
The display case of the refrigerated merchandiser of the present invention has a first air outlet disposed in its top panel that directs relatively cold refrigerated air from the merchandiser""s refrigeration compartment, cooled in a conventional manner, downwardly across the open-front viewing area of the display case to form an innermost air curtain. In addition to this first air outlet, a second air outlet is provided outwardly of the first air outlet to guide relatively warmer air generally downwardly to form an outer air curtain across the same viewing area. However, in contrast to conventional refrigeration display cases, the second air outlet includes guide vanes for directing the outer air curtain outwardly away from the inner air curtain at a divergent angle. The guide vanes may be permanently set at a predetermined divergent angle, or may be adjustable between a range of divergent angles so as to permit in-store optimumization.